Toggle-type die clamping unit of an injection molding machine

ABSTRACT

A toggle mechanism is supported at the front face of the housing and a forward end of the toggle mechanism is connected to a back face of the movable platen. Upon the closing and opening of dies, the toggle mechanism is stretched and contracted to move the movable platen forward and backward along the tie bars. An automatic control device calculates, before the dies are mounted, from a die thickness input and the kind of the dies input, such a stop position for the link housing as impart a target value to the stretching/contraction amount that the toggle mechanism has when the dies are in closed state, and calculates, from the kind of the dies input, an appropriate contraction amount greater than the target value, and the automatic controlling device moves the link housing to the stop position calculated and the toggle mechanism by the appropriate contraction amount calculated.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based upon and claims the benefit of priorityfrom the prior Japanese Patent Application No. 2002-029831, filed Feb.6, 2002, the entire contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a toggle-type die clamping unitof an injection molding machine and, in particular, to the function of,before mounting operation of dies, automatically stopping a link housingand movable platen to their appropriate positions.

[0004] 2. Description of the Related Art

[0005] In an electric injection molding machine, a toggle mechanism hasbeen widely used as a die clamping unit. A primary section of thetoggle-type die clamping unit comprises a base, a stationary platen, amovable platen, a link housing, a toggle mechanism, etc. The stationaryplaten is fixed on the base and retains a stationary die in place. Themovable platen is arranged opposite to the stationary platen andconfigured to retain the movable die and supported on the base to bemovable in forward and backward directions. The link housing is arrangedbehind the movable platen and can adjust the forward and backwardpositions on the base. The toggle mechanism is mounted on a front faceof the linked housing and its forward end is connected to a back face ofthe movable platen. Upon closing and opening of the dies, astretching/contraction amount of the toggle mechanism is controlled tomove the movable platen forward and backward.

[0006] Since, in the toggle-type die clamping unit, in order toeffectively utilize clamping force raising function of the togglemechanism, it is necessary that the position of the link housing beinitially adjusted so as to allow the stretching/contraction amount ofthe toggle mechanism to reach a predetermined target value with the diesin a closed state. If, therefore, the die thickness (a total thicknessof the stationary and movable dies in a closed state) varies, it isnecessary to adjust the stop position of the link housing each time.

[0007] At a start of a die mounting operation in a conventionalinjecting machine, the operator has initially adjusted the stoppositions of the link housing and movable platen as will be describedlater, while operating push buttons on an operation panel in a manualmode. That is, with associated dies not in a mounted state, thestretching/contraction amount of the toggle mechanism is adjusted andthen it is stopped in a state to be contracted to some extent forexample, about 10 to 20 mm from a supposed position at a die clampingtime. Then, while confirming the distance between the stationary platenand the movable platen by the eyes of the observer, the position of thelink housing is adjusted in accordance with the thickness of the diesand, in a supposed state allowing the insertion of the dies, the linkhousing is stopped.

[0008] After, in this way, the stop positions of the link housing andmovable platen have been initially adjusted, the stationary and movabledies are attached to the stationary and movable platens, respectively.Then the stop position of the link housing is finally fine-adjusted byclamping the dies by a predetermined die clamping force and, in thisstate, bringing the stretching/contraction amount of the togglemechanism up to a predetermined target value.

[0009] (Problem of the Conventional Die Clamping Unit)

[0010] In the conventional die clamping unit, as set out above, when,prior to the die mounting operation, the stop position of the linkhousing is initially adjusted so as to meet the thickness of the diesused, the operator has confirmed, by the eyes, the distance between thestationary platen and movable platen. For this reason, it is not easy toaccurately align the stop position of the link housing with theappropriate position. It also needs a cumbersome operation and it takesa lot of time to do so.

[0011] In the case where no accurate preliminary adjustment isperformed, in a final adjustment subsequent to the mounting of the dies,more steps are required so as to fine-adjust the stop position of thelink housing. And more time is needed in the final adjustment operation.

BRIEF SUMMARY OF THE INVENTION

[0012] The present invention has been achieved in view of the problemencountered in the conventional toggle-type die clamping unit and it isaccordingly the object of the present invention to provide a dieclamping unit which can accurately and efficiently perform a preliminaryadjusting operation of a link housing's position which has to be doneprior to the mounting of the dies.

[0013] A toggle-type die clamping unit of an injection molding machineaccording to the present invention comprises a base; a stationary platenfixed on the base and configured to retain a stationary die; a movableplaten arranged opposite to the stationary platen and configured toretain a movable die, the movable platen being configured to besupported on the base in such a state as to be movable in forward andbackward directions; a link housing arranged on the base behind themovable platen and adjustable in position in the forward and backwarddirections; a toggle mechanism mounted to a front face of the linkhousing and having a forward end which is connected to a back face ofthe movable platen, the toggle mechanism being configured to have itsstretching/contraction amount controlled so as to move the movableplaten forward and backward to close and open the dies; a detectorconfigured to detect a position of the link housing on the base and anautomatic controlling device configured to control a stop position ofthe link housing, wherein, before the dies are mounted, the automaticcontrolling device calculates, from a die thickness input, such a stopposition for the link housing as impart a target value to thestretching/contraction amount that the toggle mechanism has when thedies are in closed state, and the automatic controlling device moves thelink housing to the stop position calculated.

[0014] It is to be noted that the target value for thestretching/contraction amount of the toggle mechanism is so set that thedie clamping force raising function by the toggle mechanism becomes amaximal value, or its near value, when the dies are in closed state.

[0015] Preferably, a toggle-type die clamping unit of an injectionmolding machine according to the present invention has, in addition tothe detector (first detector) configured to detect the position of thelink housing on the base, a second detector configured to detect thestretching/contraction amount of the toggle mechanism, in which, beforethe dies are mounted, the above-mentioned automatic controlling devicecalculates, from a die thickness input and the kind of the dies input,such a stop position for the link housing as impart a target value tothe stretching/contraction amount that the toggle mechanism has when thedies are in closed state, and calculates, from the kind of the diesinput, an appropriate contraction amount greater than the target value,and the automatic controlling device moves the link housing to the stopposition calculated and the toggle mechanism by the appropriatecontraction amount calculated.

[0016] It is to be noted that the above-mentioned appropriatecontraction amount for the toggle mechanism is so set in accordance withthe kind of the dies as to allow the distance between the stationaryplaten and the movable platen to become a value corresponding to thethickness of the dies plus a gap necessary to the insertion of the dies.

[0017] In the case where, for example, spring-incorporated-type dies(dies incorporating springs to open the dies) are used, theabove-mentioned automatic controlling device is so configured as to,when the spring-incorporated-type dies are inputted as the kind of dies,calculate the above-mentioned appropriate contraction amount on thebasis of the opening amount of dies opened by the spring. That is, theabove-mentioned appropriate contraction amount is so set as to allow thedistance between the stationary platen and the movable platen to becomea value corresponding to the thickness of the dies opened by springsplus a gap necessary to the insertion of the dies.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0018]FIG. 1 is a view of a structure diagrammatically showing atoggle-type die clamping unit according to the present invention; and

[0019]FIG. 2 is a flow chart showing one method for preliminarilyadjusting the positions of a link housing and movable platen before themounting of dies in the toggle-type die clamping unit of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

[0020]FIG. 1 shows a structure diagrammatically showing a toggle-typedie clamping unit of an injection molding machine according to thepresent invention.

[0021] In the Figure, reference numeral 1 shows a stationary platen; 2,a movable plate; 3, a link housing; 4, a toggle mechanism; 5, tie bars;6, a stationary die; 7, a movable die; 10, a base; 11, an encoder (asecond detector); and 12, a displacement detector (a first detector).

[0022] The stationary platen 1 and link housing 3 are arranged to faceeach other on a base 10. The stationary platen 1 is fixed on the base10. The stationary platen 1 and link housing 3 are coupled to each otherby four tie bars 5. A threaded portion is provided at an area of the tiebar where it extends through the link housing 3. A nut 17 on thethreaded portion of each tie bar 17 is attached to the link housing 3.By driving the nut 17, a positional adjustment of the link housing 3 ismade in forward and backward (right and left) directions on the base 10.The position of the link housing 3 is detected by means of thedisplacement detector 12 mounted on the base 10.

[0023] The movable platen 2 is arranged between the stationary platen 1and the link housing 3. The tie bars 5 pass through the four cornerportions of the movable platen 2, respectively. The movable platen 2 canbe moved back and forth on the base 10. The stationary die 6 is attachedto the front surface (to the left in the Figure) of the stationaryplaten while the movable die 7 is attached to the front surface (to theright in the Figure) of the movable platen 2.

[0024] The toggle mechanism 4 is attached to the front face of the linkhousing 3. The forward end of the toggle mechanism 4 is connected to aback face of the movable platen 2. Upon closing and opening of the dies,the stretching/contraction amount of the toggle mechanism 4 iscontrolled to allow the movable platen to be moved forward and backwardalong the tie bars 5. The stretching/contraction amount is controlled bydriving a ball screw 21 through a pulley 18, a timing belt 20 and pulley19 with the use of a servomotor 16 and, by doing so, moving a crosshead22 forward and backward along the tie bars 5. The stretching/contractionamount of the toggle mechanism 4 is detected by the encoder 11 attachedto the servomotor 16.

[0025] In connection with this toggle-type die clamping unit, anexplanation will be made below about one method for preliminarilyadjusting the positions of the link housing 3 and movable platen 2before the mounting of the dies. FIG. 2 shows a flow chart of thepreliminary adjustment in supposing the case of mounting aspring-incorporated-type dies, that is, the dies with springsincorporated to open the dies. It is to be noted that, in FIG. 2, “LH”denotes the link housing and “MP” denotes the movable platen.

[0026] Before mounting the dies 6 and 7, an unit operator selects a “diemounting” mode on an operation panel and then inputs the die thicknessand springing amount (a die opening amount by the springs) as inputdata. Then, the operator depresses an “automatic die thicknessadjustment” button. By doing so, the input data is conformed and acorresponding LED starts to be flashed on and off.

[0027] An automatic control device, not shown, of the die clamping unitdetermines a stop position (XSL12L in the Figure) of the link housing 3based on the inputted die thickness and springing amount so that thestretching/contraction amount of the toggle mechanism 4 in a die-closedstate reaches a predetermined target value. On the other hand, anappropriate value (XSL12 in the Figure) of the stretching/contractionamount of the toggle mechanism 4 before the mounting of the dies is sodetermined that a distance between the stationary platen 1 and themovable platen 2 becomes a value corresponding to the thickness of thedies opened by the springs plus a gap necessary to insertion of thedies.

[0028] When the operator again depresses the “automatic die thicknessadjustment” button, the corresponding LED is lighted and the linkhousing 3 and movable platen 2 start to be moved. The automatic controldevice of the die clamping unit, while detecting the position of thelink housing 3 by the displacement sensor 12, moves the link housing 3to the appropriate position (XSL12L) set out above. At the same time, itmoves the movable platen 2 to the above-mentioned appropriate position(XSL 12) while detecting the stretching/contraction amount of the togglemechanism 4 by the encoder 11.

[0029] After the link housing 3 and movable platen 2 have been broughtto their appropriate positions and stopped there, the LED is turned OFFand the preliminary position adjusting operation of the link housing 3and movable platen 2 has been completed.

[0030] Although, in the above-mentioned example, it is supposed that thespring-incorporated-type dies are mounted, if normal-type dies (dies notincorporating springs to open the dies) are mounted, it is not necessaryto consider the opening amount by the springs. That is, the appropriatevalue (XSL12) of the stretching/contraction amount of the togglemechanism 4 before the mounting of the dies is determined such that thedistance between the stationary platen 1 and the movable platen 2becomes a value corresponding to the thickness of the dies in a closedstate plus a gap necessary to the insertion of the dies.

[0031] According to the toggle-type die clamping unit of the injectionmolding machine according to the present invention, it is possible toaccurately and efficiently make an adjusting operation of preliminarilyadjusting the positions of the link housing and movable platen beforethe mounting of the dies.

What is claimed is:
 1. A toggle-type die clamping unit of an injectionmolding machine comprising: a base; a stationary platen fixed on thebase and configured to retain a stationary die; a movable platenarranged opposite to the stationary platen and configured to retain amovable die, the movable platen being configured to be supported on thebase in such a state as to be movable in forward and backwarddirections; a link housing arranged on the base behind the movableplaten and adjustable in position in the forward and backwarddirections; a toggle mechanism mounted to a front face of the linkhousing and having a forward end which is connected to a back face ofthe movable platen, the toggle mechanism being configured to have itsstretching/contraction amount controlled so as to move the movableplaten forward and backward to close and open the dies; a detectorconfigured to detect a position of the link housing on the base and anautomatic controlling device configured to control a stop position ofthe link housing, wherein, before the dies are mounted, the automaticcontrolling device calculates, from a die thickness input, such a stopposition for the link housing as impart a target value to thestretching/contraction amount that the toggle mechanism has when thedies are in closed state, and the automatic controlling device moves thelink housing to the stop position calculated.
 2. A toggle-type dieclamping unit of an injection molding machine comprising: a base; astationary platen fixed on the base and configured to retain astationary die; a movable platen arranged opposite to the stationaryplaten and configured to retain a movable die, the movable platen beingconfigured to be supported on the base in such a state as to be movablein forward and backward directions; a link housing arranged on the basebehind the movable platen and adjustable in position in the forward andbackward directions; a toggle mechanism mounted to a front face of thelink housing and having a forward end which is connected to a back faceof the movable platen, the toggle mechanism being configured to have itsstretching/contraction amount controlled so as to move the movableplaten forward and backward to close and open the dies; a first detectorconfigured to detect a position of the link housing on the base; asecond detector configured to detect the stretching/contraction amountof the toggle mechanism; and an automatic controlling device configuredto control a stop position of the link housing and thestretching/contraction amount of the toggle mechanism, wherein, beforethe dies are mounted, the automatic controlling device calculates, froma die thickness input and the kind of the dies input, such a stopposition for the link housing as impart a target value to thestretching/contraction amount that the toggle mechanism has when thedies are in closed state, and calculates, from the kind of the diesinput, an appropriate contraction amount greater than said target value,and the automatic controlling device moves the link housing to the stopposition calculated and the toggle mechanism by the appropriatecontraction amount calculated.
 3. A toggle-type die clamping unitaccording to claim 2, wherein the automatic control device calculatesthe appropriate contraction amount when the type of dies inputdesignates spring-incorporated-type dies incorporating springs, saidappropriate contraction amount being corresponding to an opening amountof the dies opened by the springs.